Resolution of each screen view of a computer display system is a function of two components. One component is the computer software which is executed by the computer and which outputs signals for the screen view. The other component is the monitor or display unit itself which receives the screen view signals from the computer. Typically a display controller is used to hold screen view signals output from the computer and to reformat and transmit the signals in a timely manner to continually refresh the display unit screen.
With the various software programs and monitors available today, different combinations of software, display controllers and display units are made. Where the software requires for its output a certain pixel resolution of the receiving screen (monitor) and the monitor has a larger pixel resolution, correction is needed. Additionally, it is often useful to be able to display very high resolution continuous tone images on a monitor, but such high resolution for displaying graphics on the same monitor is unnecessary. This is especially the case where a high resolution image display unit, for example a typical 19 inch screen of 2560 pixels by 2048 pixels, hence 200 DPI (dots per inch), and PC software, which typically requires a receiving screen pixel resolution of 75-100 DPI, are utilized together to display graphics (i.e. user editorial markings and text) overlays on grey scale or color images.
Another problem involves the demands placed on the display controller. The memory in the display controller must not only continuously refresh the monitor screen but also must have sufficient bandwidth so that new data can be loaded into the memory quickly. One solution is to employ a video-random-access-memory (VRAM) in the display controller in a wide-word dual-ported configuration. The VRAM has a memory matrix for holding data (screen view signals) and a cooperating high speed serial interface which transfers a multiplicity of pixel data at a time and frees the memory for access while simultaneously transmitting screen view signals. The VRAMs however are expensive.
Accordingly, there is a need for a computer display system that provides high resolution image display in an inexpensive, and diverse software and hardware compatible manner.